高效降解木质纤维素的白蚁肠道微生物组

Gut microbiome of wood-feeding termites

摘要:

木食性白蚁是自然界木质纤维素的高效降解者，在长期进化过程中白蚁与其肠道微生物组协同作用发展出不同的纤维素降解机制。木食性白蚁具有分别来源于白蚁和共生微生物的两套纤维素酶系统。在低等白蚁中，木质颗粒经过白蚁前、中肠分泌的内源性酶初步消化后，在后肠共生鞭毛虫中被降解为乙酸、二氧化碳和氢。高等木食性白蚁在进化中丢失了鞭毛虫，木质颗粒经白蚁自身分泌的酶初步消化后，在后肠大量共生细菌的帮助下被有效降解。培菌类白蚁利用其菌圃中的蚁巢伞菌和肠道微生物协同作用降解木质纤维素。共生微生物在白蚁的氮素固定与循环、中间产物代谢及纤维素降解等过程中发挥了重要作用。学习和模拟白蚁高效降解木质纤维素的体系，对生物质能源的产业化发展具有积极的意义。

关键词:白蚁;肠道;微生物组;纤维素降解;共生

Abstract:

Termites are efficient lignocellulose degraders in the natural ecosystem. During the long-time evolution, termites have developed different strategies to decompose lignocellulose efficiently with the help of their gut microbiome. Wood-feeding termites have duel-cellulolytic systems that originated from termites and their microbiota. In lower termites, wood particles are digested primarily by endogenous cellulase secreted from the host foregut and midgut and then decomposed almost completely by numerous flagellates in the hindgut of termites. The fermentation products are acetate, carbon dioxide and hydrogen. Wood-feeding higher termites lost flagellates during the evolution. Wood particles are digested primarily by endogenous cellulase secreted from the host and are subsequently degraded by symbiotic bacteria in the hindgut of the termites. Fungus-cultivating termites degrade wood particles with the help of Termitomyces they cultivated in the fungus combs and their intestinal microbiota. The symbiotic microbiota in termite guts may involve in bioprocess like nitrogen fixation and uric acid hydrolyzation, utilization and transformation of metabolic intermediates, and degradation of lignocellulose. It is meaningful to study and imitate the highly efficient lignocellulose-degrading system of termites for biofuel industry development.

Key words:termites;gut;microbiome;lignocellulose-degradation;symbiosis